PB95-963156
EPA/AMD/R05-95/286
February 1996
EPA Superfund
Record of Decision Amendment:
Mid State Disposal Site,
Marathon County, WI
8/4/1995
-------
ROD AMENDMENT
MID STATE DISPOSAL SITE
MARATHON COUNTY, WISCONSIN
Introduction
The United States Environmental Protection Agency (U.S. EPA) is changing the remedy
selected in the Original Record of Decision (ROD) dated September 30, 1988.
•v.
The Mid-State Disposal site consists of a 30-acre landfill, the. old mound Area, a 7-acre
interim expansion landfill, and a 3-acre sludge lagoon (Figure 1). During the period of its
operation from 1970 to 1979, .the Mid-State Disposal site received domestic, industrial,
commercial, and institutional wastes, as well as construction and demolition debris. These
wastes included papermill sludges, coating sludges, fly ash, asbestos dust, mineral core waste,
glue waste, solvents, pesticides, paint sludges, and heavy metals.
The ROD signed in September of 1988 selected the following remedy:
a landfill cap which meets the requirements of Chapter NR 500 of the
Wisconsin Administrative Code (WAQ,
an active gas extraction system and condensate collection system,
improvements to site drainage,
an alternate water supply (AWS)
site monitoring for groundwater, surface water and landfill gas,
off-site treatment of leachate,
site fencing and sign posting for security,
on-site road construction, and
institutional controls.
A Consent Decree in the matter of United States of America v. Mid State Disposal Inc et
aLiWas entered into on March 28, 1990; whereby the agreement allowed for the Remedial
Design/Remedial Action (RD/RA) to be performed by the Settling Defendants and oversight of
such RD/RA by U.S. EPA and WDNR.
-------
AWS SOW WEU.
GROUNOWATER HC
WEU. INSTALLS) I
REMEDIAL INVEST*
GROUNOWATER IK
WELL INSTALLED I
PflC-OCSGN STU
PROJECT/CUENT
MID-STATE WASTE DISPOSAL SITE
WELL tOCATlON DIAGRAM
AFVKCND 9t \ T.W.W
-------
The need to collect additional information to facilitate remedial design was recognized in the
ROD and a Pre-design Study was completed in 1991. The remedial design was completed in
1993, with construction completed in the Spring of 1994. Of the nine remedial components
noted above, all except Component 4, the AWS, have been implemented or initiated as part of
the Operation and Maintenance.
As provided for in section 300.515(e) of the National Oil and Hazardous Substances Pollution
Contingency Plan (NCP) a public comment period with the opportunity for a public meeting
was held from June 16, 1995 through July 15, 1995. In addition to the public comment
period, the nine residents on Big Rapids Road were sent letters explaining how the changes
presented in this document would affect them individually. No comments were received
during the public comment period.
This ROD Amendment will become part of the Administrative Record pursuant to the NCP
Section 300.825 (a)(2) including responses to comments received during the public comment
period and the public meeting (if requested by the public). The Administrative Record can be
found at the site repository located at:
Marathon County Public Library
Stratford Branch
300 East Larch Street
Stratford, Wisconsin 54484
Reasons for Issuing the ROD Amendment
During the course of the Pre-design activities, an initial hydrogeologic evaluation of the area
around the site was completed to address the potential of establishing high-capacity water
supply wells. The results of this study indicated that an AWS consisting of two upgradient
wells was not a feasible alternative. The results of the study were discussed in a report
entitled, Proposed Alternate Water Supply System April 16, 1991. Complete results of the
initial hydrogeologic investigation for the AWS component of the remedy were presented in
the Pre-Design Report, Appendix J, dated October 18, 1991. The findings are briefly
summarized below.
Based upon the review of area geology and hydrogeology, and the estimate of the residents'
water needs, three locations were identified as potentially having the geology and location
favorable for development of an AWS. These three sites were 1) Big Rapids County Park
adjacent to the Eau Pleine River, located 2-1/4 miles west of the nearest potential receptor; 2)
the confluence of Rock Creek and Big Eau Pleine River next to the abandoned railroad trestle,
approximately 1-1/2 miles south of the nearest residence; and, 3) Fenwood Creek where it
crosses County Trunk Highway P, approximately 1-1/4 miles from the nearest residence.
-------
Results of a geophysical seismic survey conducted at each of the three sites indicated that the
site with the greatest potential for development of a large capacity supply well(s) in
unconsolidated deposits was the Big Rapids Park site.
However, the deposits encountered in the test borings at the Big Rapids Park site were judged
to be of insufficient permeability to support a public supply well. Water consumption
estimates based on information from the 9 residents affected indicated a supply well was
needed that could generate 100 gallons/minute. The deposits encountered at the Big Rapids
site were estimated to yield only 10 gallons/minute maximum.
Given that peak water demands typically occur, according to well established cycles in the
dairy industry and households, the possibility of incorporating a water storage system to store
water during periods of low usage was investigated. This element was determined not to be
feasible for the following reasons:
1. Even with a storage system, the water-bearing deposits believed most suitable
for an AWS would produce less than the estimated requirement of 15,691
gallons per day.
2. The potential for malfunction would be high, especially during extremely cold
winter months.
Based on the lack of a sufficiently thick water bearing for an AWS, additional evaluation of
hydrology and water quality was undertaken. The AWS Final Scope of Work (SOW) was
prepared to provide the additional data necessary to evaluate the hydrology and water quality
which would provide a trend analysis on which a decision regarding the construction of the
AWS could be based.
The AWS Scope of Work
The objective of this study was to provide a consistent and reliable data base upon which a
decision regarding the construction the AWS could be based. Specific data requirements
included:
1. Groundwater quality information sufficient to evaluate groundwater quality
trends over time and to assist in evaluating hydrogeologic conditions at the site.
2. Groundwater elevation data to evaluate groundwater and contaminant
movement, particularly in the area of the groundwater divides.
3. Additional hydrogeologic information in the area encompassed by the two
groundwater divides.
-------
•ASLC 1
ALTERNATE WATFR SUPPIY ANALYTICAL PARAMETERS
MIO-*TATE DISPOSAL SITE
3ARAMETE9
•••OCi
Vmvi Chlonda
Ci«*1 .2-0>cMoroatnana
Chloroform
1 ,2-OicMaroorooana
' 3-Oiehtarooreoana
T»tfacnioroatnana
Naontnaian*
'.1.1- Tricrtoroatnana
' 2-OicMoroamana
.hlorooanzana
s-Kooroovitoluana
1 .2-DichloroBanzana
rt-eutytbamxana
1 4-Oicttarooaniana
HaxacHorobutaoiana
1 ,2-O«bromo'3-Chlorooropan«
2-CMorate*uan*
1 , 1 ,2-TricrHoroainana
tart^utylbantana
1 . 1 .2,2-Tatracniereatnana
Maca.fc Para> Xviana *
Ortho-Xvtan* *
8remoo«nx«n*
satti^ir"^
CKbromocmoramMt^n.
SvnoQata) Racovarv, % (PIO/HALU
NOTES:
Mfl 1«O
ES
0.2
10OO
aso
ISO
70
9
5
5
5
343
5
10
2OO
•j
10O
aoo
75
100
.
OJ
0.8
o.os
fl2O
420
700
215
179
•JB 140
002
200
95
15
7
o.e
o.s
0.5
0.5
08.8
0.5
8
•) 5
20
40
IS
10
;
0.02
0.08
0.005
124
124
140
43
38
JSEPA
MCL
2
5
70
100
5
5
O.S
1000
5
200
•i
10O
000
78
too
70
0.2
5
O.OS
10.000
—
70O
— •
10O
100
METHOD
36TECTION
JMIT
0.4S
0.48
0.27
0.33
0.15
0.45.
0.24-..
0.27
0.33
0.24
0.13
0.13
0.27
0.1S
0.24
0.18
0.21
0.12
0.21
0.12
O.18
0.18
0.12
0.21
0.27
0.12
0.12
0.18
0.19
0.27
0.18
0.27
0.38
0.18
0.88
0.15
0.27
0.12
0.3
0.24
0.48
• STANDARD..
aEPOBJINC"'
LIMIT
2.0
2.0
1.0
1.0
1.0
1.0
1.0
2.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
10
1.0
1.0
t 0
1.0
1.0
2.0
1.0
2.0
1 0
1.0
'•0
1.0
1.0
1.0
1.0
1.0
1. * » No PAL: NoE-S.
2. • ES. PAL and MCL (or wMnM «oo*Y to total rvtww eoneamraoon.
3. UCL » Manmtxn Contamnant Laval (or puoac warar tyatam*.
4. — . No MCL
UMk!atata/82e8SXJ/202.xJa/MLH-4c/rav.
-------
TABLE 1. com.
INORGANIC AND INDICATOR PARAMETERS
ALTERNATE WATER SUPPLY ANALYTICAL PARAMETERS
MID-STATE DISPOSAL SITE
PARAMETER
METALS, uo/t
Arsenic
Barium
Cadmium
Chromium
Copper
Iron
Leaa
Manganese
Mercury
Selenium
Stiver
NR140
ES
50
2000
5
100
1300
300
15
50
2
50
50
NR 140
PAL
5
400
0.5
10
130
150
1.5
25
0.2
10
10
INSTRUMENT
USEPA DETECTION
MCL LIMIT
50
2000
5
100
1300
300'
15
2
50
1.0
0.7
1.0
3.4
52
12.4
1.0
0.5
0.1
2.0
8.7
1. A -NoPAL: NoE.3.
2. * - MCL tor iron is a secondary maximum contaminant level (this is not a health based standard).
3. — . No MCL
K:MidStata/8268SXJO04JctsAILR-OCA«v. 1 11/11/94
-------
-
a
~
1S5B
J1GIMD
WELL DESIGNATION
,„„• IMTERPOLATED PK70MEUR "EAD COtlNTOUR LINE
(BASED ON JUNE 13. 1993 WATER LEVEL MEASUREMENT)
souncr uses IOPOGRAPHIC MAf. SIHATFORH ouAnnANctr. oAit
f
s ,
EC C
5
rfr
t*n
i
B2sar.
In TOOT i
\aa—
r— K
-------
r"— .--•:
-. —
&&• \ iiav
jjT^M *
"I\ ./^v* •• -r^S"
i! ^?X\^:-
r«V" '**rT^;
rr. ^^
irU •- ; N \ i
/ r '1 \ / ~ \i
Figure 3
PIEZOMETRIC HEAD DISTRIBUTION
AND GROUNDWATER FLOW DIAGRAM
IN BEDROCK AQUIF1ER
MID-STATE WASTE DISPOSAL SITE
OCDSD BT
J.M.T.
J.U.T.
CADTU
82685602 I i
WhjoiiT NO.
82685XJ
-------
The data needs were satisfied by installation of additional weils at the Mid-State site and
completion of six rounds of groundwater sampling and analysis.
The AWS SOW monitoring consisted of collection of water level data at each background and
on-site monitoring well, and collection and analysis of groundwater samples from the
background wells and selected on-site and nine residential wells on a quarterly basis for six
rounds. Figure 1 .presents a site diagram showing the locations of the background wells and
on-site monitoring wells. Figure _2_ shows the location of each of the nine residential wells
relative to the Mid-State site. Figure JL shows the location of the groundwater divides and
their relationship to the monitoring wells and the landfill areas.
Background Wells: Background wells are located up-gradient to the site which is generally
considered north of the site (wells MW-16, MW-27, and MW-31). In addition to indicator
parameters, background wells were tested for Volatile Organic Compounds (VOCs) and metals
(Table 1). Various VOCs were detected sporadically and hi various sample rounds. Most hits
were accounted for as being laboratory artifacts or were also found in the quality control
samples such as the field blanks. There were several detects of low level VOCs not
attributable to laboratory QC samples, but they were not confirmed in following rounds.
Therefore VOC results from the background wells did not affect the interpretation of VOC
data from the monitoring wells or residential wells.
Iron, Mercury, Lead and r^rfminm were detected sporadically during the 6 sampling rounds
(Table 2). In the case of Mercury, Lead and Cadmium, these compounds exceeded their
respective Preventative Action Limits (PALs)- [as per NR140 Wisconsin Administrative Code
(WAC)] only once during the 6 rounds and therefore do not effect the interpretation of the on-
site well data. Manganese was consistently detected above the Enforcement Standard (ES) (as
per NR140 WAC) in the three background wells. Remedial Investigation data also suggests
that on-site wells and residential wells have PAL and ES exceedances as well. However,
since the background wells are significantly upgradient of any on site sources it can be
concluded that the manganese concentration is a natural occurrence for this area. Also, given
the fact that Manganese, like iron, is a public welfare standard, the concentrations do not
present a threat to public health.
Monitoring Wells: On-site groundwater quality has been evaluated by sampling and analysis
of 20 monitoring wells located either hydraulically downgradient of the fill areas or sludge
lagoon, or located within the fill areas.
Metals: Evaluation of the on-site groundwater data shows localized impacts of iron at two of
the 20 wells tested. The most significant iron concentration has been observed at MW-9.
However, wells deeper and downgradient of MW-9 show no indication of elevated iron
concentrations. Therefore, the higher concentration of iron at MW-9 is likely associated with
a localized iron source. MW-30 also showed elevated iron concentrations, however statistical
analysis demonstrated a decreasing trend in the concentrations. As iron is a public welfare
-------
Table 2
HMtONOM IUMMAKT Of IKTM IXCIIOANCf S
Of WOMAMO PAftAMniM
M.1f WMTIWM1N *UmV MMTIMO
MD4TA1I DMTfMAl Mil
IUr«> m 1*41
UW 1
uwt
Mwi
MWI
Cwio
UWM
uwii
UW 11
UW 110
UW I4»
UW It
MW It
UW Itll
UWII
uwio
UW III
ww iii?
nw i«n
Sw i»H
HW ll>?
UW 1*11
i*
ROUND 1 ROUND 1 ' MOUND 3
IS f*l l» »« '» »*l
C4II 111
C« II 4 II
-- cI>»BI
i. mit.ri
M., 1101*11 C«ll.*ir MB|»«.»»| l.l«>**.ri.MM**.»MI
•••" f;iiioi" • '" c«imi • *•»«»! uiiMi.fi
MnHltn MnllMtfl
. MnlOOMl
C«ll.4 II
HOUND 4 MOUND & . MOUND «
is rm is r*i is ru
*b«.d«o< AD«I*»»« Ak««MnM
N«i ••M*i«4 N«t ••*wl*4
C4 It 1 II
F.imoooi ciiit.4i r
-------
Table 3
IIMMM MMMf •» B»M UCIIMMII
•ItlUMn fMtM
•••1411
MUMD1
icinti C'tcxiMi i jocPti li ICI It ii. I.I.I'C« »t ji «P it •). i.i o» 10 • a
It 14* M It .11. D»CP II t JI I.IDCrilOl.OCMIII M
I.IOCIIOI JI PCI 14 II PCI H II lot l« I JI Co 1.1 OCIII01
' " icl 10 t ji.'pci iili PCI it 41. we ii ji ici li ii'" ~ 'vcioiji ici ii«. PCI ii.ii we ii.n iii ii i. " tint'* vciiti icl 14 n u w ti ji. vc it«. icl «i4i.'
PCI II II . PCI 14 • Ptllt.tl
II PCI II 01
MOT II VClOtJ. PCIUIIJI
MOT II OtCPMVJ) VCII.II> PCIW.tJI*
MM no ici it 11 fci it PI tiio%jt i.totin4i vc it ti. KI it 01. PCI it 4t ru 101 ji vcit 41. tcim.>i. uiin vcit.n. ici noti un.ii vc 11 n ici 1101. unn vc i4.»i ici it n. tinti
PCI lit 41 PCI 111 II PCI HOI PCI It II
MOT 140 PCI 10 I JI _
MOT i4t pr i 16 i ji " pciibtji pciw'iji pcTio!t~ji " pciiotiJi '" " ~ ui ioit"jTfclitli
MOT l«t • PCI IIJI ,
UOTIIO PCIIItl*
•V.itii
iiol ...... -
itOI • < I OCI 10 t JI
TCE (0.9J) - Trichlorocthcnc detected at u
tniraated concentration of 0.9 ug/l
J - Estimated Value Compound detected below
die quanliution limit
TCE - Trichloroethene
VC - Vinyl Chloride
DCM - Methyleue Chloride
PCE - Tetrachloroethene
BCM - Bromochloromethane
1,2 DC A -1,2 Dichloroethane
1,1 DCE -1,1 Dichloroetheoe
1,2 DCE - 1.2 Dkhloroetheue
1.1.2TCA - i.1.2 Trichloroethane
1,2 DCP - -1,2 Dichloropropane
DBCP - 1,2 Dibromo }-chloropropane
BZ - Benzene
CF Chloroform
ES - NR 140 Enforcement Standard
PAL - NR 140 Preventive Action Limit
* - Exceeciance in one of two duplicates only
-------
standard, not a public health standard, the level is established for aesthetic reasons and
therefore the concentrations pose no threat to public health.
Cadmium was detected at many of the on-site monitoring wells only once in most wells. It
appears that the presence of Cadmium is due to either seasonable variation or post-sampling
contamination. Cadmium was never found to exceed the ES. In accordance with NR140
WAC, an acceptable action in such a situation is continued monitoring for cadmium.
Chromium was also detected sporadically at the site, but never exceeded the ES. This
parameter will also be included in the monitoring program. PAL and ES exceedances for
metals can be found in Table 2.
VOCs: VOCs for which PAL and ES exceedances were consistently observed were limited to
vinyl chloride (VC), tetrachloroethene (PCE), trichloroethene (TCE), and benzene. PAL and
ES exceedances were observed in samples collected from site monitoring wells, as shown in
Table _3__. These wells for the most part were located inside of the groundwater divides. In
general, the four VOCs of concern have not been consistently detected in wells outside the
divides with the exception of MW-18, MW-19 and MW-31. PCE and VC exceeded their
PALs once in well MW-19. However follow-up samples did not confirm die presence of these
compounds and the original detections occurred in only one of two samples taken from that
well. MW-31 had the same scenario as MW-19. PCE was detected once during the sampling
rounds and was present in only one of two samples taken from that well. MW-18 had one
PCE PAL exceedance but was detected 4 other times below the PAL. Statistical analysis was
performed on up-gradient wells to determine if an increasing trend was present for this
contaminant. Linear regression analysis performed on the data for VC, Benzene, TCE, and
PCE for wells MW-6, MW-10, MW-22D, and MW-24S showed no statistically supported
trend of increasing concentrations. For data values below the quantitation limit (which is the
case for most PAL levels), the variability is likely due to the error inherent in measurements
below quantifiable levels. Since PCE was detected (below quantitation limits) consistently in
MW-18, it has been included in the long-term monitoring plan. The concentrations of VC,
benzene, TCE, and PCE at MW-10 do appear to be generally increasing with time. MW-10 is
located just east of the southeast corner of the fill area, and northwest of the intersection of the
two groundwater divides. The confirmed presence of contaminants in samples drawn from
MW-10 is of concern because MW-10 is located along the groundwater divide and north of the
residential wells. Samples from downgradient wells MW-22S, MW-29, and MW-23 have not
shown evidence of contaminant impacts downgradient of MW-10. Wells MW-23 and MW-29
lie between MW-10 and the receptors to the south and east. MW-23 and MW-29 are both
included in the long-term monitoring program and will serve as early indicators if
contaminants begin to move toward the residences.
Residential Wells: Residential groundwater quality has been monitored at nine residential
wells located along Big Rapids Road to the south, southeast, and southwest of the site.
Exceedances of PALs and ESs for metals or VOCs have not been consistently observed in
-------
TABLE 4
RESIDENTIAL WELL DATA ROUNDS 1 THROUGH 3 '
Well No.
RW-1558
RW-1593
RW-1617
RW-1677
RW-1707
RW-1763
RW-1813
RW-1834
RW-1861
Round 1
Metals
Fe 33.0 EB
Fe 10.3 EB
Fe 53.7 EB
Fe 8.5 E
Fe11.6E
Fe612E
Fe 15.7 E
Fe 15.0 E
Fe 20.5 E
Round i
VOCs
DCM 1.0 U
DCDFM 1.7 J
BZ 0.4 J
Round 2
Metals
Fe 23.2 E
Fe 14.3 E
Round 2
VOCs
NPH 0.7 E
NPH 0.7 E
111-TCA 07 U
NPH 0.6 E
Styrene 0.2 E
111-TCA 1.2 U
111-TCA 0.3 U'
111-TCA 0.4 U
111-TCA 0.3 U
Round 3
Metals
Fe 17.6 U
Fe 34.4 U
Cd 1.4 E"
Fe 19.8 U'
Fe 7.6 U
/
Fe 20.5 U
Round 3
VOCs
n-PB 0.4 E
NPH 0.8 U
t-B 1.1 U
DCM 0.9 U
t-B 1.1 U
DCM 10*
t-B 0.5 U'
Tol 0.2 U*
124TMB 0.4 E"
NPH 1.1 U
t-B 1.1 U
DCM 1.0U
BZ 0.3 E
2CT 0.1 E
Tol 0.3 U
NPH 0.9 U
t-B 04 U
DCM 0.4 U
t-B 0.3 U
BZ 1.5
iPB 03 E
NPH 1.0 U
t-B 0.6 U
Tol 0.3 U
NPH 13 U
t-B 0.2 U
NPH 0.8 U
t-B 0 3 U
-------
TABLE 4 (continued)
RESIDENTIAL WELL DATA ROUNDS 4 THROUGH 6
Well No.
RW-1558
RW-1593
RW-1617
RW-1677
RW-1707
RW-1763
RW-1813
RW-1834
RW-1881
Round 4
Metals
Fe 53.0 U
Fe 38.8 U
Fe 11.4 U
Fe 46.6 U
Fe34.1 U
Cd 1.3 E*
Fe 33.6"
Cr 7.1'
Fe 58.2 E
Round 4
VOCs
DCM 1.0 U
t-B 0.4 U
DCM 2.1 U
NPH 0.3 J
DCM2.1U
DCM 2.6 U
t-B 0.2 U
2CT0.1J
t-B 0.3 U
DCM 1.7 U
DCM 2.3 U
DCM 2.3 U*
PCE 0.6 U'
t-B 0.2 U"
DCM 1.7 U
t-B 0.2 U
DCM 2.1 U
Round 5
Metals
Fe164
Fe 15.6 U
Fe 65.2 U
Fe228
Fe 10.1 U
Fe 52.8 U
Fe 21.7 U
Fe 36.0 U
Fe 16.9 U
Round 5
VOCs
DCM 4.0 U
t-B 0.2 U
DCM 3.8 U
Tol 0.2 U
t-B 0.2 U
Tol 0.2 U
DCM 5.5 U
DCM 5.5 U
Tol 0.2 U
DCM 3.5 U
DCM 3.8 U
DCM 4.6 U*
BZ 2.4*
111-TCA0.2U'
t-B 0.3 U"
DCM 4.2 U
t-B 0.29 U
DCM 5.3 U
Tol 0.16 U
t-B 0.18 U
Round 6
Metals
Fe 13.4 U
Fe 18.5 U
Fe 43.3 U
Fe 14.3 U
Fe 37.2 U
Fe 20.5 U*
Fe21.6U
Round 6
VOCs
DGM 1.9U
NPH 03 J
t-B 02 U
DCM 2.1 U
t-B 0.2 U
t-B 0.3 U
DCM 1.6 U
DCM 4.1 U
NPH 0.3 U
t-B 0.2 U
BZ 0.26 J
I-B0.17U
DCM 0.94 U
PCE 0.15 J
t-B 0.15 U
DCDFM 1.4 J
DCM 1.1 U
DCM 1.5 U"
t-B 0 3 U"
DCM 1.3 U
t-B 0.28 U
DCM 1.1 U
t-B 0.31 U
-------
TABLE 4 LEGEND
DCDFM = Dichlorodiflouromethane Cd = Cadmium
111-TCA * 1,1,1-Trichkxoethane Fe = Iron
2CT = 2-Chloroto!uene Cr = Chromium
1,2,4-TMB = 1,2,4-Trimethylbenzene DCM = Methylenechloride
PCE = Tetrachloroethene BZ = Benzene
i-PB = Isopropylbenzene NPH = Naphthalene
t-B - tert-butylbenzene Tol = Toluene
n-PB = n-Propylbenzene o-X = ortho-Xylene
Notes
Units are in ug/L
B = Analyte also detected in a laboratory blank
U = Analyte detected at a comparable concentration in one or more blanks.
E = Concentration is below the contract required detection limit.
J = Concentration is an estimated value below the quantitation limit
' = Highest result of replicates
' = Detected in one of the replicates only.
-------
samples drawn from the residential wells, with the exception of well 1813. A summary of
parameters detected in residential well samples throughout the six rounds of the AWS is
presented in Table JL- Generally, iron appears to be a naturally occurring element at the site
and is a common laboratory contaminant at low levels; and t-butylbenzene and methylene
chloride are confirmed laboratory contaminants These three analytes were detected in nearly
every sample (including background samples) and blank submitted for each round. Other
analytes detected in residential well samples and background samples included: naphthalene;
1,1,1-trichloroethane, toluene, 2^hlorotoluene, dichlorodiflouromethane, styrene, ortho-
xylene, PCE and benzene. Results indicate that these VOCs are present as laboratory
contamination. Repeated use of these constituents in the laboratory creates a potential source
of contamination. With the exception of Benzene as discussed below, none of the above VOCs
were detected consistently in any residential well or on-site monitoring well sample. Data
validation procedures and intra-well comparisons indicate that reported concentrations of these
analytes may represent false positives or analytical noise, or were introduced as post-sampling
contaminants. Therefore, the data suggests that these VOCs are not site contaminants.
The intra-well and upgradient well comparisons performed for the residential wells support
evidence of contamination at only one residential well; that being the apparent presence of
benzene in RW-1813. However, comparison of the benzene data at RW-1813 to benzene
concentrations at upgradient wells (MW-23, MW-29) indicates that the Mid-State Landfill is
probably not the source of benzene contamination at RW-1813. However to ensure the
validity of this theory and to ensure safe drinking water to this resident, RW-1813 will be
included in the long-term sampling plan.
Conclusions drawn from the AWS SOW:
Based on the data collected during this study, it can be stated that groundwater data continues
to support the groundwater flow pattern presented in previous reports, in particular the lack of
groundwater mounding below the site and the existence of two groundwater divides on the
Mid-State site. The first divide (east-west) inhibits groundwater flow from the fill areas to the
south towards the nearest residents. The second divide (north-south) limits flow to the east.
Given the position of the two divides and the absence of groundwater mounding below the fill
areas, the primary direction of flow from below the fill areas continues to be towards the west.
(FigureS)
Groundwater quality in the monitoring wells and residential wells has been consistent with
time when the AWS data is compared to the RI and pre-design data. Affected groundwater
has not migrated off-site so as to create adverse exposure to area residential wells. No
consistent site related contamination has been detected during the study in the residential wells.
The selected remedy components currently in-place should improve groundwater quality over
time due to reduced infiltration as a result of the cover, VOC removal via the leachate seep
collection system and active gas extraction system, and a probably southward shift hi die east-
-------
west divide as a result of reduced infiltration.
Based on the information obtained above, there appears to be no need for the provision of an
alternate water supply at this time.
Amended Alternative
No Alternative Water Supply with a contingency for point of use systems in the event that
a degradation of water quality is demonstrated.
A contingency plan will be implemented for a particular resident if the same target compound
is detected above its Enforcement Standard in each of two or more samples collected from that
particular residential well during two different sampling rounds.
The owner and/or user of the residential well will be notified by the WDNR of the first
Enforcement Standard exceedance and the re-sampling date. If the second sample collected is
also above an Enforcement Standard and the data is unqualified, the contingency plan will be
implemented.
Users of potentially affected residential wells will be supplied with bottled water for human
consumption within 48 hours of a first ES exceedance. If the ES exceedance is verified by the
second sample, a long-term protective measure will be implemented. If livestock are affected,
an interim water supply for livestock will also be provided. If the target compound is detected
in the verification sample at a concentration exceeding the Enforcement Standard, a point-of-
use treatment systems, as described below will be installed at the affected residences as a long
term measure.
Based on the successful implementation of point of use treatment systems at other sites, the
WDNR approves the use of such systems. The system hardware will consist of granulated
activated carbon (GAC) treatment systems permitted by the Department of Industry, Labor and
Human Relations and the WDNR. The main components of a suitable GAC system are a
water meter, valves situated between the system components for ease of removal, sampling
ports, three 14-inch by 72 inch GAC treatment vessels, and the existing pressure tank.
Operation and Maintenance per the manufacturer specifications is also necessary for proper
operation of the system. The treatment vessels contain 5 cubic feet of granular activated
carbon each. The three vessels operate in series supplying a flow rate of 10 g.p.m. with a
contact time of 10 to 15 minutes.
The VOC compounds will be adsorbed on the GAC media. If inorganics are a concern, ion
exchange system or other appropriate treatment method will be utilized. As the available
pores in the GAC media become occupied, the media will eventually become saturated and a
"breakthrough" condition will occur. At breakthrough, VOC compounds will begin to pass
through the treatment system. Regular monitoring of the system will be conducted to
-------
8
determine when breakthrough occurs.
The GAC cartridges will be exchanged before breakthrough contaminants reach a drinking
water quality standard or Enforcement Standard. Monthly monitoring of systems will be
conducted for the first year of operation. The sampling frequency will then be reduced to
quarterly sampling.
A maTimnm of two samples will be collected monthly for each treatment unit. One sample
will be taken before the first treatment unit, and one sample will initially be taken after the
first treatment unit to monitor breakthrough of the first GAC canister. When the second
sample indicates that breakthrough has occurred hi the first canister, the second sample will be
taken between the second and third canisters for the next sampling period. When the sample
taken between the second and third canisters indicates breakthrough, the third canister will be
moved to the 1st position and the new or regenerated 1st and 2nd canister will be moved to the
second and third canister positions.
GAC cartridges are also subject to biofouling, which can result in clogging of the cartridge
and/or undesirable bacteria and organic mass in the outflow. Monitoring for, or maintenance
to avoid biofouling will be conducted in accordance with the manufacturer's recommendations.
Therefore, should biofouling occur, the third canister will be moved to the first position and
the first and second canisters would be replaced.
IMPORTANT NOTE: LONG TERM MONITORING WILL CONTINUE FOR 30
YEARS.
The wells to be sampled in the long term monitoring plan were chosen to provide a spatial
distribution around the disposal areas and to target the main discharge areas consistent with
WAC NR508. Sampling at these well locations will provide the data necessary to evaluate the
effectiveness of the remedy and monitor for the possibility of off-site movement of affected
groundwater. Based also on spatial distribution and data collected during the 6 rounds of the
Alternate Water Supply Study, Residential wells 1707, 1763,1813, and 1834 are included hi
the long term monitoring plan. These wells are closest to the site and as in the case of RW
1813, have had intermittent detects of contaminants These contaminant levels are not a health
risk and cannot be confirmed as being from the landfill (as explained in the results section),
but to be conservative, these wells will continue to be monitored. The wells will be sampled
quarterly for the first two years in accordance with NR508.10(3) and the Consent Decree.
Thereafter, sampling will be performed semi-annually. In addition, every five years,
functioning wells will be sampled for field pH, temperature, and conductivity: VOCs and 8
RCRA metals. After five (5) years of sampling, the sampling frequency, location and analyses
requirements will be evaluated as part of the statutory 5-year performance review. Any
changes made to the sampling program must be approved by U.S. EPA and WNDR. The
sampling program will be evaluated every 5 years during the thirty years of its existence.
Wells to be monitored during the long term monitoring plan are shown in Table _5_-
-------
Table 5
Long-Term Groundwater Monitoring
Locations. Frequency, and Trigger Wells
Mid-Slate Disposal SKe
STS Project No. 82685XJ
Monitoring Well
Well 1.0.
MW-3
MW-4
MW-5
MW-6
MW-7
MW-6
MW-9
MW-10
MW-11
MW-12
MW-13
MW-14
MW-15
MW-16S
MW-16D
MW-17
MW-18
MW-19
9^Q W W I *»
MW-22S
MW-22D
MW-23
MW-24S
MW-24D
MW-2S
MW-26S
MW-26D
MW-27
MW-28
MW-29
*Vv v v ft0W
MW-30
MW-31S
MW-31D
Residential Wells
RW-1707
RW-17S3
RW-1813
RW-1834
Monitoring Freauencv
Once/5 Years
Once/5 Years
Once/5 Years
•
Once/5 Years
Once/5 Years
Once/5 Years
•
Once/5 Years
Once/5 Years
Once/5 Years
•
Once/5 Years
Once/5 Years
Once/5 Years
•
Sami-annually m
Sarni-annuailv *"
^^^9v«*i ^fti BV MvCUl W
•
•
•
•
•
Once/5 Years
•
•
Once/5 Years
Once/5 Years
•
•
*
•
•A
•A
•A
•A
Trigger
Well
Yes
Yes
Yes
Yes
1 ww
Yes
Yes
TO9
Yes
Trigger Mechanism
3 Consecutive PAL Exceedances (1)
-fc..
3 Consecutive PAL Exceedances {1>
3 Consecutive PAI. ExC9£danc&S P)
3 Consecutive PAL Exceedarms ^'
%^%M •v^*«M^M V 0 ( *^W bAwWWU4UlwO<3
3 Consecutive PAL Exceedances n)
3 Cfinspmth/a PAL P*w>«vlanrfts f
W WWiiM9\«Ull* W • rl^ ^AvV^JMOl i*m&
3 Consecutive PAL Exceedances 0>
•
Motes:
* - Wells to be monitored quarterly for 2 years and semi-annuaJty thereafter.
* - Monitoring frequency at this location may be modified, depending on groundwater quality
at the trigger wells.
(1) - Refers to 3 consecutive PAL Exceedances of a health-based NR140, WAC groundwater
quality standard.
121 = Well will be tested for VOCs. cadmium, iron and chromium only.
277,05
-------
Overall protection of Human Health and the Environment - The amended alternative and the
original alternative are considered protective of human health and the environment given the
additional information documented in die AWS study. No adverse effects to the water supply
are anticipated. As stated above, the amended alternative includes groundwater quality
monitoring, and a provision through which treatment of water if water quality should
deteriorate would be implemented.
Compliance with ARARs - With the other components of the final remedy for the Mid-State
landfill in-place, the amended remedy and the original remedy are equivalent \vith regard to
their compliance with the ARARs. Contaminant levels in the residential wells are well below
the enforceable and health based levels which renders the original alternative unnecessary at
this time. Each alternative includes long-term monitoring to detect changes in on and off-site
groundwater quality. With both alternatives, ARAR NR140 would require additional action if
results of the long-term monitoring demonstrated NR140 Enforcement Standard exceedances at
any of the residential wells.
Long-Term Effectiveness and Permanence - A significant residual risk does not exist with
either the amended remedy or the original remedy. The original remedy, which relies on a
remote source of water, would remain unaffected even if unforeseeable significant changes in
the contaminant and groundwater flow regime occur, although this is not anticipated. The
amended alternative entails no residual risk at present and unlikely will entail residual risk in
die future based on the source control measures already instituted at the site and the additional
water quality and hydrogeologic data collected since the RI. If significant and unforeseeable
changes in the pattern and distribution of the contaminants occur, these would be detected by
the long-term monitoring program and appropriate actions, as stated in the contingency plan
component of the amended alternative, would be taken. The original remedy requires
extensive and permanent (beyond 30 years) operation and maintenance.
Reduction of Toxicity. Mobility and Volume Through Treatment - Neither Alternative provides
a reduction in mobility, toxicity and volume through treatment. This has been achieved
through those parts of the original remedy already performed.
Short-Term Effectiveness - The original alternative would have the greatest short-term impacts
on the environment, community and workers during implementation due to pipeline
construction. Wetlands are present in the site area and their locations would have to be
identified and taken into consideration for pipeline location and construction. The amended
alternative would have no short-term effects on the environment or community.
Tmnlementability - The amended alternative is technically feasible. The original remedy as
specified in the FS is not technically feasible given the local unconsolidated sediments are not
of sufficient thickness or quality to provide a reliable water supply for nine residents and their
farms.
-------
10
Costs. - The original alternative may require land acquisition or permanent easements. An
access road would be required which would entail long term operation and maintenance. The
capital cost would be approximately $248,000 and the O&M would be $194,000.
For the amended alternative, no inconvenience to the residences would be involved and the
there would be only cost associated with sampling and analytical analysis. The contingency
portion of this alternative would cost approximately $134,000 and O&M would be $69,000.
State Acceptance - In recent years, point-of-use treatment as described in the contingency
portion of the amended alternative has been implemented at other sites in Wisconsin and has
been demonstrated to be effective and acceptable to the residents involved. After review of
these additional case studies, the WDNR has adopted the stance that point-of-use treatment
systems are acceptable in a limited number of situations, including the Mid-State site. The
original alternative would not be acceptable since it is not technically feasible. The amended
alternative would be acceptable to WDNR since it is protective of human health and the
environment.
Community Acceptance - The residents whose wells have been part of the AWS scope of work
sampling program have been notified after every quarterly sampling event with the results of
the data from their wells. In addition, after the AWS 6 sampling rounds had been completed,
letters were sent to each resident describing the overall findings of the sampling rounds in
relation to their personal well and the site. A one page questionnaire regarding their feelings
on the alternate water supply and communications during the site work was sent out. One
response was received out the nine sent indicating that they were in favor of eliminating the
AWS as long as they would still be protected if conditions changed. They also indicated that
they were pleased with the information provided by U.S. EPA. No comments were received
during the public comment period.
Amended Remedy
Based on the performance of the amended remedy against the nine evaluation criteria
previously discussed and die additional data collected during the Pre-Design Study and AWS
SOW Study, U.S. EPA believes that the amended remedy as described in this document (no
alternative water supply) is the most appropriate solution for the Mid-State site.
Statutory Determinations
Overall Protection of Human Health and the Environment:
This amended remedy combined with the actions already taken is overall protective of human
health and the environment. The contingency plan provides a means of additional, rapidly
implementable protection to human health, should enforcement standard exceedances at
designated trigger wells indicate adverse changes in site conditions.
-------
11
Attainment of ARARs:
Since other components of the remedy have been implemented and available data indicates that
groundwater quality off-site has not been adversely affected, the amended remedy currently
complies with ARARs. It will also be effective in.both the long-term and short-term. The
long-term groundwater monitoring systems will serve as an early indicator of any change that
may develop. The contingency plan included in the amended remedy provides for continued
compliance with ARARs, should results of the long-term monitoring indicate deterioration of
off-site groundwater quality.
*...
Cost Effectiveness:
The amended remedy provides overall cost effectiveness. The only cost that would be
incurred with this remedy is the analytical cost associated with long-term monitoring. Should
conditions change, the contingency plan included in this remedy is also cost effective.
Implementation is not a problem and no costs will be incurred to treat uncontaminated
groundwater or to supply water to residential homes who's water supplies are uncontaminated.
Utilization of Permanent Solutions and Alternative Treatment Technologies or Resource
Recovery Technologies to the Maximum Extent Practicable:
The amended remedy, in combination with the work already performed, provides a permanent
solution to the maximum extent practical for this site.
Preference for Treatment as a Principle Element:
Because no health based levels were exceeded off-site and the positions and performance of the
groundwater divides have been verified, treatment of the principle threat posed by the
groundwater on-site was not found appropriate or practical.
The statutory five-year review will continue for that portion of the remedy already performed
(Landfill cap, leachate and gas collection system) as this results in hazardous substances
remaining on-site. This review is scheduled for March 31, 1998.
fi
^"""'
Valdas V. Adamkus
Regional Administrator
------- |